Hand finishing a stone is often done rather than ultrasonic due to a certain stone or gems unstable or hydroscopic nature making it unable to be wet finished or oil treated without damaging the color of the stone or gem. It is widely known that turquoise and opal are often worked and finished dry or cabbed by hand and hand polished or buffed dry to avoid color or property changes. Enhancements which naturally increase hardness and stability are often used to maintain value without introduction of harsh chemicals. One method used is the Zachary method which uses silica (naturally found in turquoise) and adds more of this natural substance to non chemically stabilize the beautiful mineral without taking away the natural beauty or using chemical or plastic binders which devalues the stones drastically. COMPLETELY untreated stones are the most valuable and rare & due to the often unstable property of natural stones of certain types, the hand working or hand polishing (dry-method) is often used.
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